Plated, Injection Molded, Automotive Radar Waveguide Antenna

ABSTRACT

The radar system includes a split-block assembly comprising a first portion and a second portion. The first portion and the second portion form a seam, where the first portion has a top side opposite the seam and the second portion has a bottom side opposite the seam. The system includes at least one port located on a bottom side of the second portion. Additionally, the system includes radiating elements located on the top side of the first portion, wherein the radiating elements are arranged in a plurality of arrays. Yet further, the system includes a set of waveguides in the split-block assembly configured to couple each array to at least one port. Furthermore, the split-block assembly is made from a polymer and where at least the set of waveguides, the at least one port, and the plurality of radiating elements include metal on a surface of the polymer.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Radio detection and ranging (RADAR) systems can be used to activelyestimate distances to environmental features by emitting radio signalsand detecting returning reflected signals. Distances to radio-reflectivefeatures can be determined according to the time delay betweentransmission and reception. The radar system can emit a signal thatvaries in frequency over time, such as a signal with a time-varyingfrequency ramp, and then relate the difference in frequency between theemitted signal and the reflected signal to a range estimate. Somesystems may also estimate relative motion of reflective objects based onDoppler frequency shifts in the received reflected signals.

Directional antennas can be used for the transmission and/or receptionof signals to associate each range estimate with a bearing. Moregenerally, directional antennas can also be used to focus radiatedenergy on a given field of view of interest. Combining the measureddistances and the directional information allows for the surroundingenvironment features to be mapped. The radar sensor can thus be used,for instance, by an autonomous vehicle control system to avoid obstaclesindicated by the sensor information.

Some example automotive radar systems may be configured to operate at anelectromagnetic wave frequency of 77 Giga-Hertz (GHz), which correspondsto a millimeter (mm) wave electromagnetic wavelength (e.g., 3.9 mm for77 GHz). These radar systems may use antennas that can focus theradiated energy into tight beams in order to enable the radar system tomeasure an environment with high accuracy, such as an environment aroundan autonomous vehicle. Such antennas may be compact (typically withrectangular form factors), efficient (i.e., with little of the 77 GHzenergy lost to heat in the antenna or reflected back into thetransmitter electronics), and low cost and easy to manufacture (i.e.,radar systems with these antennas can be made in high volume).

SUMMARY

Disclosed herein are embodiments that relate to methods and apparatusesfor a radar system. The radar system includes a split-block assemblycomprising a first portion and a second portion. The first portion andthe second portion form a seam, where the first portion has a top sideopposite the seam and the second portion has a bottom side opposite theseam. The system further includes at least one port located on a bottomside of the second portion.

Additionally, the system includes a plurality of radiating elementslocated on the top side of the first portion, wherein the plurality ofradiating elements is arranged in a plurality of arrays. Yet further,the system includes a set of waveguides in the split-block assemblyconfigured to couple each array to at least one of the at least oneport. Furthermore, the split-block assembly is made from a polymer andwhere at least the set of waveguides, the at least one port, and theplurality of radiating elements include metal on a surface of thepolymer.

In another aspect, the present application describes a method of forminga waveguide antenna unit. The method includes forming a first portion ofa split-block assembly from a polymer, where the first portion comprisesa plurality of radiating elements located on a top side of the firstportion, and where the plurality of radiating elements is arranged in aplurality of arrays. The method also includes forming a second portionof the split-block assembly from the polymer, where the second portioncomprises at least one port on a bottom side of the second portion.Additionally, the method includes forming a metal surface on at least afirst region of the first portion and a second region of the secondportion. Yet further, the method includes assembling the split-blockassembly by coupling a bottom side of the first portion and a top sideof the second portion to form a seam, where the coupling forms anelectrical connection between the first portion and the second portion.The seam may define a center of a set of waveguides in the split-blockassembly. The set of waveguides are configured to couple each array toat least one of the at least one port. In addition, at least the set ofwaveguides, the at least one port, and the plurality of radiatingelements comprise metal.

In yet another example, a radar system is provided. The radar systemincludes a radiating assembly having a plurality of portions, where eachportion is made from a polymer. The radar system further includes a portformed in at least one of the plurality of portions. The port may belocated on a bottom side of the radiating assembly. Additionally, thesystem includes a plurality of radiating elements formed in at least oneof the plurality of portions. The radiating elements may be located on atop side of the radiating assembly. And, the plurality of radiatingelements may be arranged in a plurality of arrays. Yet further, thesystem includes a set of waveguides in the radiating assembly configuredto couple each array to at least one of the at least one port.Furthermore, the set of waveguides, the at least one port, and theplurality of radiating elements comprise metal on a surface of thepolymer.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the figures and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates an assembled view of the top of an example antenna,in accordance with an example embodiment

FIG. 1B illustrates an assembled view of the bottom of an exampleantenna, in accordance with an example embodiment

FIG. 1C illustrates an example isometric cross-section view of awaveguide having a metallic portion

FIG. 1D illustrates an example isometric cross-section view of awaveguide having a metallic portion

FIG. 1E illustrates an example isometric cross-section view of awaveguide having a metallic portion

FIG. 2A illustrates a first layer of an example antenna, in accordancewith an example embodiment

FIG. 2B illustrates a second layer of an example antenna, in accordancewith an example embodiment

FIG. 3 illustrates an example power coupler, in accordance with anexample embodiment

FIG. 4 illustrates conceptual waveguide channels formed inside anassembled example antenna, in accordance with an example embodiment

FIG. 5 illustrates an example wave-radiating portion of an exampleantenna, in accordance with an example embodiment

FIG. 6 illustrates a method of forming a waveguide antenna unit inaccordance with an example embodiment

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying figures, which form a part hereof. In the figures, similarsymbols typically identify similar components, unless context dictatesotherwise. The illustrative embodiments described in the detaileddescription, figures, and claims are not meant to be limiting. Otherembodiments may be utilized, and other changes may be made, withoutdeparting from the scope of the subject matter presented herein. It willbe readily understood that the aspects of the present disclosure, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

The following detailed description relates to an apparatus and methodsfor a radar antenna array that is constructed of a polymer material. Theradar antenna array may be formed via an injection molding process.Because a conventional polymer would not conduct electromagnetic energyin the radio frequency (RF) portion of the radar antenna array well, atleast a portion of the polymer surface of the radar antenna array may becoated with a metal in order to achieve a sufficient level ofperformance for the radar unit. The metal coating may be applied tovarious surfaces of the radar antenna array by many different processes.In some examples the metal coating may be allied through electroplating.In other examples, the metal coating may be applied through electrolessplating or physical vapor deposition. Generally, the metallic layer hasat least the thickness of a skin depth of the signal that will propagatethrough the waveguide. In practice, because of the high frequency ofoperation, the skin depth is relatively thin. Therefore, theabove-discussed plating processes can produce a metallic layer ofsufficient thickness for the waveguide operation.

A radar antenna array of an autonomous vehicle may include a pluralityof antennas. Each antenna may be configured to (i) transmitelectromagnetic signals, (ii) receive electromagnetic signals, or (iii)both transmit and receive electromagnetic signals. The antennas may forman array of antenna elements. Each antenna of the array may be fed(i.e., supplied with a signal) from a waveguide. Additionally, thewaveguide may communicate signals received by the various antennas to areceiver within the radar system. Additionally, a circuit board locatedoutside of the antenna unit may communicate signals to and from theantenna unit. As used herein, the terms electromagnetic energy,electromagnetic signals, signals, electromagnetic waves, and waves maybe used interchangeably to denote the electromagnetic energy that isused with the systems and methods.

The following detailed description may be used with an apparatus havingan antenna array that may take the form of a single-input single-outputsingle-input, multiple-output (SIMO), multiple-input single-output(MISO), multiple-input multiple-output (MIMO), and/or synthetic apertureradar (SAR) radar antenna architecture. The radar antenna architecturemay include a plurality of “dual open-ended waveguide” (DOEWG) antennas.In some examples, the term “DOEWG” may refer herein to a short sectionof a horizontal waveguide channel plus a vertical channel that splitsinto two parts, where each of the two parts of the vertical channelincludes an output port configured to radiate at least a portion ofelectromagnetic waves that enter the antenna. Additionally, a pluralityof DOEWG antennas may be arranged into an antenna array. The radarantenna architecture described herein may include a plurality of antennaarrays.

An example antenna architecture may comprise, for example, two layers,each formed by an injection molding process, and can have a metalcoating formed on the RF components of each layer of the antenna. Forexample, the RF components may include the input port, the waveguides,and the radiating element (i.e. antenna elements), and each may each becoated with metal. Conventional antenna architectures for radar unitsare formed of metal (e.g., aluminum plates) that can be machined by wayof computer numerical control (CNC) and joined together. By switching toan injection molding process, the antenna units may be built moreinexpensively, in less time, with tighter tolerances, and with a lowerweight. The antenna units made through the injection molding process mayfeature the same or similar geometries for various components (such asthe RF components) of the antenna unit as conventional CNC milledantenna units. The antenna units disclosed herein may be fabricated byway of an injection molding process to make a plastic cast of theantenna. At least a portion of the plastic cast may be plated with metalto create the functional RF components of the antenna.

The first layer of the antenna unit may include a first half of an inputwaveguide channel, where the first half of the first waveguide channelincludes an input port that may be configured to receive electromagneticwaves (e.g., 77 GHz millimeter waves) into the first waveguide channel.The first layer may also include a first half of a plurality ofwave-dividing channels. The plurality of wave-dividing channels maycomprise a network of channels that branch out from the input waveguidechannel and that may be configured to receive the electromagnetic wavesfrom the input waveguide channel, divide the electromagnetic waves intoa plurality of portions of electromagnetic waves (i.e., power dividers),and propagate respective portions of electromagnetic waves to respectivewave-radiating channels of a plurality of wave-radiating channels. Afterhaving metal plating applied, the two layers may be assembled togetherto form a split-block assembly.

In various examples, the power dividing elements of the antennaarchitecture may be a two- or three-dimensional dividing network ofwaveguides. The dividing network of waveguides may use waveguidegeometry to divide power. For example, the feed waveguides may have apredetermined height and width. The predetermined height and width maybe based on a frequency of operation of the radar unit. The dividingnetwork may include waveguides that differ in height and/or width fromthe predetermined height and width of the feed waveguides in order toachieve a desired taper profile.

In the present disclosure, feed waveguides that provide a signal toradiating elements (i.e. antenna elements) may be divided between thetop and bottom portions of the split-block assembly. Further, the feedwaveguides may all be located in a common plane where the midpoint ofthe height of feed waveguides is common for all of the feed waveguides.The dividing network of waveguides may be located partly in the sameplane as the feed waveguides and partly in at least one other plane. Forexample, the entire height of a portion of the dividing network ofwaveguides may be molded into either the first or second portion of thesplit-block assembly. When the two block pieces are brought together, asurface of the other block portion may form an edge of the portion orthe dividing network of waveguides that has its height fully in one ofthe two block sections. In some examples, the vertical portion of thesewaveguide cavities and cuts are symmetric with respect to the splitblock seam.

When operating a waveguide system, various signals may be propagatedthrough the waveguide system. The waveguide system may include a networkof waveguides each with at least one antenna element on the top surfaceof the antenna block. Conventionally, each antenna element would radiatea portion of the electromagnetic energy fed to it.

A waveguide is a structure that conducts electromagnetic energy from onelocation to another location. In some instances, conductingelectromagnetic energy with a waveguide has the advantage of having lessloss than other conduction means. A waveguide will typically have lessloss than other conduction means because the electromagnetic energy isconducted through a very low loss medium. For example, theelectromagnetic energy of a waveguide may be conducted through air or alow loss dielectric.

In one embodiment, such as an air-filled waveguide, the waveguide willhave a metallic outer conductor (e.g., metal plating on the moldedplastic surface). The size and shape of the waveguide define thepropagation of the electromagnetic energy. For example, electromagneticenergy may bounce (or reflect) off the metallic walls of waveguide.Based on the shape and the materials of the waveguide, the propagationof the electromagnetic energy will vary. The shape and the materials ofthe waveguide define the boundary conditions for the electromagneticenergy. Boundary conditions are known conditions for the electromagneticenergy at the edges of the waveguide. For example, in the metallicwaveguide, assuming the waveguide walls are nearly perfectly conducting,the boundary conditions specify that there is no tangentially directedelectric field at any of the wall sides. Once the boundary conditionsare known, Maxwell's Equations can be used to determine howelectromagnetic energy propagates through the waveguide.

Maxwell's Equations may define several modes of operation for any givenwaveguide. Each mode has one specific way in which electromagneticenergy can propagate through the waveguide. Each mode has an associatedcutoff frequency. A mode is not supported in a waveguide if theelectromagnetic energy has a frequency that is below the cutofffrequency. By properly selecting both (i) waveguide dimensions and (ii)frequency of operation, electromagnetic energy may propagate through thewaveguide in a specific mode. Often, waveguides are designed so only onepropagation mode is supported at the design frequency.

There are four main types of waveguide propagation modes: TransverseElectric (TE) modes, Transverse Magnetic (TM) modes, TransverseElectromagnetic (TEM) modes, and Hybrid modes. In TE modes, theelectromagnetic energy has no electric field in the direction of theelectromagnetic energy propagation. In TM modes, the electromagneticenergy has no magnetic field in the direction of the electromagneticenergy propagation. In TEM modes, the electromagnetic energy has noelectric or magnetic field in the direction of the electromagneticenergy propagation. In Hybrid modes, the electromagnetic energy has someof both electric field and magnetic field the direction of theelectromagnetic energy propagation.

TE, TM, and TEM modes can be further specified using two suffix numbersthat correspond to two directions orthogonal to the direction ofpropagation, such as a width direction and a height direction. Anon-zero suffix number indicates the respective number ofhalf-wavelengths of the electromagnetic energy equal to the width andheight of the waveguide. However, a suffix number of zero indicates thatthere is no variation of the field with respect to that direction. Forexample, a TE₁₀ mode indicates the waveguide is half-wavelength in widthand there is no field variation in the height direction. Typically, whenthe suffix number is equal to zero, the dimension of the waveguide inthe respective direction is less than one-half of a wavelength. Inanother example, a TE₂₁ mode indicates the waveguide is one wavelengthin width (i.e. two half wavelengths) and one half wavelength in height.

When operating a waveguide in a TE mode, the suffix numbers alsoindicate the number of field-maximums along the respective direction ofthe waveguide. For example, a TE₁₀ mode indicates that the waveguide hasone electric field maximum in the width direction and zero maxima in theheight direction. In another example, a TE₂₁ mode indicates that thewaveguide has two electric field maxima in the width direction and onemaximum in the height direction.

Example systems within the scope of the present disclosure will now bedescribed in greater detail. An example system with which the radarantenna array is formed by metal plating a plastic injection-moldedarray may be used, implemented, or may take the form of an automobileradar system, a system to test radar capabilities of an automobile radarsystem, or any other type of waveguide system. Additionally, examplesystems may be implemented in other vehicles, such as cars, trucks,motorcycles, buses, boats, airplanes, helicopters, lawn mowers, earthmovers, boats, snowmobiles, aircraft, recreational vehicles, amusementpark vehicles, farm equipment, construction equipment, trams, golfcarts, trains, and trolleys. Other systems that use waveguides can alsoinclude a radar antenna array injection molded in plastic and havingmetal plating.

FIG. 1A illustrates an assembled view of the top of an example antenna100, in accordance with an example embodiment. The example antenna 100may include a first layer 110 and a second layer 120. The second layer120 may include a plurality of holes 112 (through-holes and/orblind-holes) configured to house alignment pins, screws, and the like.The first layer 110 may include a plurality of holes as well (not shown)that are aligned with the holes 112 of the second layer 120. The twolayers may join at a common plane (i.e. the two layers may be joined ata seam).

As shown in FIG. 1A, an array 106 may include an array of DOEWGradiating elements 102, the number and position which may vary based onthe number of DOEWGs and channels of the antenna 100. The radiatingelements 102 of the DOEWG array may be a linear array (as shown), atwo-dimensional array, a single element, or other configuration ofradiating elements.

In some examples, the antenna 100 may include a transmission array 106and a reception array 108. As previously discussed, the RF components,including the various elements of each array, may be plated with metalafter initially being made through an injection molding process.Further, in an example embodiment, components other than the RFcomponents may also be plated with metal. For example, a top and bottomsurface of the antenna block may be coated with metal. In variousexamples, different metallic coatings are possible as well.

In some embodiments, the first and second layers 110, 120 may beinjection molded from plastic and may be at least 3 mm in thickness(e.g., about 5.84 mm to 6.86 mm). Additionally, the second layer 120 maybe injection molded to a thickness of about 3.886 mm. Other thicknessesare possible as well.

In some embodiments, the joining of the two layers 110, 120 may resultin an air gap or other discontinuity between mating surfaces of the twolayers. In such embodiments, this gap or discontinuity may be proximateto (e.g. as close as possible to) a center of the height of the antennaapparatus and may have a size of about 0.05 mm or smaller. Further, anadditional thickness of metal may be plated on one or both surfaces inorder to reduce or remove the air gap.

FIG. 1B illustrates an assembled view of the bottom of an exampleantenna 140, in accordance with an example embodiment. The antenna 140may be the bottom of antenna 100 shown in FIG. 1A. As shown, the firstlayer 110 may include a plurality of holes 142 (through-holes and/orblind-holes) configured to house alignment pins, screws, and the like.One or more of the plurality of holes 142 may be aligned with the holesof the second layer 120. Further, FIG. 1B shows two ports 144, 146 inthe first layer 110. The ports 144, 146 may be where the antenna 140receives electromagnetic waves into the one or more waveguide channelslocated within the antenna 140. The ports 144, 146 may also be where theantenna 140 couples electromagnetic waves from the one or more waveguidechannels located within the antenna 140 to subsequent processing. Insome examples the ports 144, 146 may be bidirectional, configured tocouple signals into and out of the antenna 140.

FIG. 1C illustrates an example isometric cross-section view of awaveguide 150 having a metallic portion 153A, 153B. The examplewaveguide 150 is formed with a top portion 152 and a bottom portion 154.The top portion 152 and a bottom portion 154 are coupled at seam 156.The waveguide includes a cavity 158. Within cavity 158, electromagneticenergy propagates during the operation of waveguide 150. The waveguide150 may also include a feed 159. Feed 159 can be used to provideelectromagnetic energy to cavity 158 in waveguide 150. Alternatively oradditionally, feed 159 may be used to allow electromagnetic energy toleave waveguide 150. The example waveguide 150 of FIG. 1C features seam156 at the middle point of the height of cavity 158. In variousembodiments, the top portion 152 and a bottom portion 154 may be coupledtogether at various different positions along an axis of the waveguide.

As shown in FIG. 1C, the top portion 152 and the bottom portion 154 mayhave a respective metallic portion 153A, 153B. The metallic portion 153Aof the bottom portion 154 and the metallic portion 153B of the topportion 152 may each be formed through a plating process. As previouslydiscussed, both the top portion 152 and the bottom portion 154 may bemade of a polymer. The respective metallic portions 153A, 153B may beplated onto the RF surfaces, such as the internal portion of cavity 158and the port 159. Thus, when the top portion 152 is brought into contactwith the bottom portion 154, there is an electrical coupling of therespective metal portions. In the example shown in FIG. 1C, only the RFsurfaces are plated. In other examples, such as those described withrespect to FIGS. 1D and 1E, additional surfaces beyond just the RFsurfaces may be plated as well.

FIG. 1D illustrates an example isometric cross-section view of awaveguide 160 having a metallic portion 153C, 153D. The waveguide 160may be similar to the above-described waveguide 150, except waveguide160 has different plating. The top portion 152 and the bottom portion154 may have a respective metallic portion 153C, 153D. The metallicportion 153C of the bottom portion 154 and the metallic portion 153D ofthe top portion 152 may each be formed through a plating process. Aspreviously discussed, both the top portion 152 and the bottom portion154 may be made of a polymer. The respective metallic portions 153C,153D may be played across the full surface of the respective portion.For examples, the metallic portion 153C of the bottom portion 154 maycover the entire top surface of the bottom portion 154. Additionally,the metallic portion 153D of the top portion 152 may cover the entirebottom surface of the top portion 152. Thus, when the top portion 152 isbrought into contact with the bottom portion 154, there is an electricalcoupling of the respective metal portions. The internal portion ofcavity 158 and the port 159 may be plated with metal in this example.

FIG. 1E illustrates an example isometric cross-section view of awaveguide 170 having a metallic portion 153E, 153F. The waveguide 170may be similar to the above-described waveguide 150, except waveguide170 has different plating. The top portion 152 and the bottom portion154 may have a respective metallic portion 153E, 153F. The metallicportion 153E of the bottom portion 154 and the metallic portion 153F ofthe top portion 152 may each be formed through a plating process. Aspreviously discussed, both the top portion 152 and the bottom portion154 may be made of a polymer. The respective metallic portions 153E,153F may be played across the full surface of the respective portion.For examples, the metallic portion 153E of the bottom portion 154 maycover the entire top surface of the bottom portion 154. Additionally,the metallic portion 153F of the top portion 152 may cover the entirebottom surface of the top portion 152. Thus, when the top portion 152 isbrought into contact with the bottom portion 154, there is an electricalcoupling of the respective metal portions. The internal portion ofcavity 158 and the port 159 may be plated with metal in this example.

FIG. 2A illustrates a first layer 200 of an example antenna, inaccordance with an example embodiment. The dashed lines of the waveguide(used throughout) indicate the beamforming components of the feedwaveguides. In this example, first layer 200 includes a first half of aplurality of waveguide channels 202. These waveguide channels 202 maycomprise multiple elongated segments 204. At a first end 206 of eachelongated segment 204 may be a plurality of collinear wave-directingmembers 208, each with sizes similar or different from otherwave-directing members. In line with the description above, the firstends 206 of the elongated segments 204 may be referred to herein as afirst half of wave-radiating channels.

At a second end 210 of the channels 202 opposite the first end 206, oneof the elongated segments 204 may include a through-hole 212 (i.e.,input port). A given amount of power may be used to feed a correspondingamount of electromagnetic waves (i.e., energy) into the apparatus, andthe through-hole 212 may be the location where these waves are fed intothe apparatus. In line with the description above, the singlechannel/segment of the waveguide channels 202 that includes the inputport may be referred to herein as an input waveguide channel.

Upon entering the apparatus, the electromagnetic waves may generallytravel in the +x direction, as shown, towards an array of power dividers214 (i.e., a “beam-forming network”). The array 214 may function todivide up the electromagnetic waves and propagate respective portions ofthe waves to respective first ends 206 of each elongated segment 204.More specifically, the waves may continue to propagate in the +xdirection after leaving the array 214 toward the wave-directing members208. In line with the description above, the array 214 section of thewaveguide channels may be referred to herein as wave-dividing channels.

As the portions of the electromagnetic waves reach the wave-directingmembers 208 at the first end 206 of each elongated segment 204 of thewaveguide channels 202, the wave-directing members 208 may propagatethrough respective sub-portions of the electromagnetic energy to asecond half of the waveguide channels (i.e., in the +z direction, asshown). For instance, the electromagnetic energy may first reach awave-directing member that is recessed, or molded further into the firstlayer 200 (i.e., a pocket). That recessed member may be configured topropagate a smaller fraction of the electromagnetic energy than each ofthe subsequent members further down the first end 206, which may beprotruding members rather than recessed members. Further, eachsubsequent member may be configured to propagate a greater fraction ofthe electromagnetic waves travelling down that particular elongatedsegment 204 at the first end 206 than the member that came before it. Assuch, the member at the far end of the first end 206 may be configuredto propagate the highest fraction of electromagnetic waves. Eachwave-directing member 208 may take various shapes with variousdimensions. In other examples, more than one member (or none of themembers) may be recessed. Still other examples are possible as well. Inaddition, varying quantities of elongated segments are possible.

A second layer may contain a second half of the one or more waveguidechannels, where respective portions of the second half of the one ormore waveguide channels include an elongated segment substantiallyaligned with the elongated segment of the first half of the one or morewaveguide channels and, at an end of the elongated segment, at least onepair of through-holes partially aligned with the at least onewave-directing member and configured to radiate electromagnetic wavespropagated from the at least one wave-directing member out of the secondlayer.

Within examples, the elongated segment of the second half may beconsidered to substantially align with the elongated segment of thefirst half when the two segments are within a threshold distance, orwhen centers of the segments are within a threshold distance. Forinstance, if the centers of the two segments are within about ±0.051 mmof each other, the segment may be considered to be substantiallyaligned.

In another example, when the two halves are combined (i.e., when the twoinjection molded layers are joined together), edges of the segments maybe considered to be substantially aligned if an edge of the first halfof a segment and a corresponding edge of the second half of the segmentare within about ±0.051 mm of each other.

In still other examples, when joining the two layers, one layer may beangled with respect to the other layer such that their sides are notflush with one another. In such other examples, the two layers, and thusthe two halves of the segments, may be considered to be substantiallyaligned when this angle offset is less than about 0.5 degrees.

In some embodiments, the at least one pair of through-holes may beperpendicular to the elongated segments of the second half of the one ormore waveguide channels. Further, respective pairs of the at least onepair of through-holes may include a first portion and a second portion.As such, a given pair of through-holes may meet at the first portion toform a single channel. That single channel may be configured to receiveat least the portion of electromagnetic waves that was propagated by acorresponding wave-directing member and propagate at least a portion ofelectromagnetic waves to the second portion. Still further, the secondportion may include two output ports configured as a doublet and may beconfigured to receive at least the portion of electromagnetic waves fromthe first portion of the pair of through-holes and propagate at leastthat portion of electromagnetic waves out of the two output ports.

FIG. 2B illustrates a second layer 220 of an example antenna, inaccordance with an example embodiment. The second layer 220 may includea second half of the plurality of waveguide channels 202 of the firstlayer 200 shown in FIG. 2A (i.e., a second half of the input waveguidechannel, the wave-dividing channels, and the wave-radiating channels).As shown, the second half of the waveguide channels 202 may take on thegeneral form of the first half of the channels, so as to facilitateproper alignment of the two halves of the channels. The elongatedsegments of the second half 222 may include second halves of the arrayof power dividers 224. As described above, electromagnetic waves maytravel through the array 224, where they are divided into portions, andthe portions then travel (i.e., in the +x direction, as shown) torespective ends 226 of the second halves of the elongated segments 222.Further, an end 226 of a given elongated segment may include multiplepairs of through-holes 228, which may be at least partially aligned withthe wave-directing members 208 of the first layer 200. Morespecifically, each pair of through-holes may be at least partiallyaligned with a corresponding wave-directing member, also referred to asa reflecting element, such that when a given sub-portion ofelectromagnetic waves are propagated from the first layer 200 to thesecond layer 220, as described above, those sub-portions are thenradiated out of the pair of through-holes (i.e., a pair of output ports)in the −z direction, as shown. Again, the combination of a givenwave-directing member and a corresponding pair of output ports may forma DOEWG, as described above.

Moreover, a combination of all the DOEWGs may be referred to herein as aDOEWG array. In antenna theory, when an antenna has a larger radiatingaperture (i.e., how much surface area of the antenna radiates, where thesurface area includes the DOEWG array) that antenna may have higher gain(dB) and a narrower beam width. As such, in some embodiments, ahigher-gain antenna may include more channels (i.e., elongatedsegments), with more DOEWGs per channel. While the example antennaillustrated in FIGS. 2A and 2B may be suitable for autonomous-vehiclepurposes (e.g., six elongated segments, with five DOEWGs per segment),other embodiments may be possible as well, and such other embodimentsmay be designed/moldeded for various applications, including, but notlimited to, automotive radar.

For instance, in such other embodiments, an antenna may include aminimum of a single DOEWG. With this arrangement, the output ports mayradiate energy in all directions (i.e. low gain, wide beamwidth).Generally, an upper limit of segments/DOEWGs may be determined by a typeof metal used for the first and second layers. For example, metal thathas a high resistance may attenuate an electromagnetic wave as that wavetravels down a waveguide channel. As such, when a larger,highly-resistive antenna is designed (e.g., more channels, moresegments, more DOEWGs, etc.), energy that is injected into the antennavia the input port may be attenuated to an extent where not much energyis radiated out of the antenna. Therefore, in order to design a largerantenna, less resistive (and more conductive) metals may be used for thefirst and second layers. For instance, in embodiments described herein,at least one of the first and second layers may be aluminum. Further, inother embodiments, at least one of the first and second layers may becopper, silver, or another conductive material. Further, aluminum layersmay be plated with copper, silver, or other low-resistance and/orhigh-conductivity materials to increase antenna performance. Otherexamples are possible as well.

The antenna may include at least one fastener configured to join thefirst layer to the second layer so as to align the first half of the oneor more waveguide channels with the second half of the one or morewaveguide channels to form the one or more waveguide channels (i.e.,align the first half of the plurality of wave-dividing channels with thesecond half of the plurality of wave-dividing channels, and align thefirst half of the plurality of wave-radiating channels with the secondhalf of the plurality of wave-radiating channels). To facilitate this insome embodiments, the first layer, a first plurality of through-holes(not shown in FIG. 2A) may be configured to house the at least onefastener. Additionally, in the second layer, a second plurality ofthrough-holes (not shown in FIG. 2B) may be substantially aligned withthe first plurality of through-holes and configured to house the atleast one fastener for joining the second layer to the first layer. Insuch embodiments, the at least one fastener may be provided into thealigned first and second pluralities of through-holes and secured in amanner such that the two layers are joined together.

In some examples, the at least one fastener may be multiple fasteners.Mechanical fasteners (and technology used to facilitate fastening) suchas screws and alignment pins may be used to join (e.g., screw) the twolayers together. Further, in some examples, the two layers may be joineddirectly to each other, with no adhesive layer in between. Stillfurther, the two layers may be joined together using methods differentthan adhesion, such as snap fits, ultrasonic welding, heat staking, andthe like. However, it is possible that, in other examples, such methodsmay be used in addition to or alternative to any methods for joininglayers that are known or not yet known.

In some embodiments, one or more blind-holes may be formed into thefirst layer and/or into the second layer in addition to or alternativeto the plurality of through-holes of the first and/or the second layer.In such embodiments, the one or more blind-holes may be used forfastening (e.g., housing screws or alignment pins) or may be used forother purposes.

FIG. 3 illustrates an example power coupler, in accordance with anexample embodiment. The power coupler may function to divideelectromagnetic energy (i.e. power) that is in the waveguides. A powercoupler is formed between two sections of waveguides that are alignedvertically adjacent or horizontally adjacent to each other. The powercoupler may be one of the RF components that is formed of metal platedplastic.

Energy may enter the antenna through an input waveguide channel and isdivided (i.e., split) into smaller portions of energy at each powerdivider, such as power divider 370, and may be divided multiple timesvia subsequent power dividers so that a respective amount of energy isfed into each of the feed waveguides. The amount of energy that isdivided at a given power divider may be controlled by a power divisionratio (i.e., how much energy goes into one channel 374 versus how muchenergy goes into another channel 376 after the division). A given powerdivision ratio may be adjusted based on the dimensions of thecorresponding power divider. Further, each power divider and associatedpower division ratio may be designed/calculated in order to achieve adesired “power taper” at the wave-radiating channels.

Within examples, (such as that shown in FIG. 3) a technique for dividingenergy between two adjacent waveguides 374, 376 may be to use a layerwith a coupling aperture 372 such as that shown in FIG. 3. By adjustingthe size, shape, and location of the coupling aperture 372, a desiredtaper profile may be achieved. Further, two adjacent waveguides, eachlocated in a different split block section may couple to ramp section382 to form a single waveguide. The single waveguide after the rampsection may be located in the common plane of the split-block assembly380.

FIG. 4 illustrates conceptual waveguide channels 400 and other RFcomponents formed inside an assembled example antenna. Moreparticularly, the waveguide channels 400 take the form of the waveguidechannels 202 of FIGS. 2A and 2B. For instance, the channels 400 includean input port 462 to the input waveguide channel 464. The channels 400also include wave-dividing channels 466 and a plurality of radiatingdoublets 468 (i.e., a DOEWG array). As described above, whenelectromagnetic waves enter the channels 400 at the input port 462, theymay travel in the +x direction through the input waveguide channel 464and be divided into portions by the wave-dividing channels 466 (e.g., bythe power dividers). Those portions of electromagnetic waves may thentravel in the +x direction to respective radiating doublets 468, wheresub-portions of those portions are radiated out each DOEWG through pairsof output ports, such as radiating pair 470, for instance.

In a particular wave-radiating channel, a portion of electromagneticwaves may first be propagated through a first DOEWG with a recessedwave-directing member 472 (i.e., an inverse step, or “well”), asdiscussed above. This recessed wave-directing member 472 may beconfigured to radiate the smallest fraction of energy of all the membersof the DOEWGs of the particular wave-radiating channel. In someexamples, subsequent wave-directing members 474 may be formed (e.g.,protruded, rather than recessed) such that each subsequent DOEWG canradiate a higher fraction of the remaining energy than the DOEWG thatcame before it. Phrased another way, each wave-directing member 472, 474may generally be formed as a step into a horizontal (+x direction)channel (i.e., a wave-radiating channel, or the “first end” of an“elongated segment” as noted above) and used by the antenna to tune theamount of energy that is radiated vs. the amount of energy that istransmitted further down the antenna.

In some embodiments, a given DOEWG may not be able to radiate more thana threshold level of energy and may not be able to radiate less than athreshold level of energy. These thresholds may vary based on thedimensions of the DOEWG components (e.g., the wave-directing member, ahorizontal channel, a vertical channel, a bridge between the two outputports, etc.), or may vary based on other factors associated with theantenna. In some embodiments, the first and second layers may be moldedsuch that various sides of the waveguide channels 400 have roundededges, such as edge 476, 478, and 480, for example.

FIG. 5 illustrates an example wave-radiating portion 500 of an exampleantenna, in accordance with an example embodiment. The wave-radiatingportion 500 of FIG. 5 illustrates an example wave-radiating doublet ofan example antenna, in accordance with an example embodiment. Morespecifically, FIG. 5 illustrates a cross-section of an example DOEWG500. As noted above, a DOEWG 500 may include a horizontal feed (i.e.,channel), a vertical feed (i.e. a doublet neck), and a wave-directingmember 504. The vertical feed may be configured to couple energy fromthe horizontal feed to two output ports 502, each of which is configuredto radiate at least a portion of electromagnetic waves out of the DOEWG500. In some embodiments, the farthest DOEWG from the input port mayinclude a backstop at location 506. The backstop may be an end or atermination of the respective waveguide. DOEWGs that come before thelast DOEWG may simply be open at location 506 and electromagnetic wavesmay propagate through that location 506 to subsequent DOEWGs. Forexample, a plurality of DOEWGs may be connected in series where thehorizontal feed is common across the plurality of DOEWGs. FIG. 5 showsvarious parameters that may be adjusted to tune the amplitude and/orphase of an electromagnetic signal that couples into the radiatingelement.

In order to tune a DOEWG such as DOEWG 500, the vertical feed width,vfeed_a, and various dimensions of the step 504 (e.g., dw, dx, and dzl)may be tuned to achieve different fractions of radiated energy out theDOEWG 500. The step 504 may also be referred to as a reflectingcomponent as it reflects a portion of the electromagnetic waves thatpropagate down the horizontal feed into the vertical feed. Further, insome examples, the height dzl of the reflecting component may benegative, that is may extend below the bottom of the horizontal feed.

In some examples, each output port 502 of the DOEWG 500 may have anassociated phase and amplitude. In order to achieve the desired phaseand amplitude for each output port 502, various geometry components maybe adjusted. As previously discussed, the step (reflecting component)504 may direct a portion of the electromagnetic wave through thevertical feed. In order to adjust an amplitude associated with eachoutput port 502 of a respective DOEWG 500, a height associated with eachoutput port 502 may be adjusted. Further, the height associated witheach output port 502 could be the height or the the depths of this feedsection of output port 502, and not only could be a height or depthadjustment but it could be a multiplicity of these changes or steps orascending or descending heights or depths in general.

As shown in FIG. 5, height dz2 and height dz3 may be adjusted to controlthe amplitude with respect to the two output ports 502. The adjustmentsto height dz2 and height dz3 may alter the physical dimensions of thedoublet neck (e.g. vertical feed of FIG. 5). The doublet neck may havedimensions based on the height dz2 and height dz3. Thus, as the heightdz2 and height dz3 are altered for various doublets, the dimensions ofthe doublet neck (i.e. the height of at least one side of the doubletneck) may change. In one example, because height dz2 is greater thanheight dz3, the output port 502 associated with (i.e. located adjacentto) height dz2 may radiate with a greater amplitude than the amplitudeof the signal radiated by the output port 502 associated with heightdz3.

FIG. 6 illustrates a method 600 of constructing an example antenna. Themethod 600 may begin at block 602 by forming a first portion of asplit-block assembly from a polymer. At block 604, the method 600includes forming a second portion of a split-block assembly from thepolymer. The first and second portions may each be one of the top andbottom portions of the previously-described waveguide antennas. Therespective portions may be formed through a polymer (e.g. plastic)injection molding process. Through the injection molding, the variousstructures of each respective waveguide portion can be formed. In somefurther examples, the final antenna may include more than two portionsas described here. In some examples, blocks 602 and 604 may involveconstructing more than two portions to create the final antenna. Forexample, some antennas may be constructed with three (or more) layers orportions. Additionally, in order to reduce weight, the plastic portionsmay further be hollowed out after the molding process.

In practice, injection molding may allow the various features of theantenna to be construction with more precise tolerances and with fewerrestrictions on geometry as compared to conventional CNC machiningprocesses. For example, some features may be created by injectionmolding that are not possible (or commercially practical) to create viaCNC processes. In various examples, each half may be molded with thedesired final dimensions for the various features of the antenna.Because the metal plating (applied at block 606) is relatively thin, itwill not significantly change the dimensions of the various elements towhich plating is applied.

At block 606, the method 600 includes forming a metal surface on atleast a first region of the first portion and a second region of thesecond portion. The RF component of the antenna, including at least theset of waveguides, the at least one port, and the plurality of radiatingelements may be coated with metal. As previously described, a frequencyof operation of the antenna may be 77 GHz. At this frequency a skindepth (the depth at which signals propagate into a metal surface) isapproximately 0.25 micron. If the thickness of the metal plating is lessthan a skin depth, it may create some undesired effects when propagatinga signal. In practice, a layer at least four or five times as thick asthe skin depth may be used to make sure the metal is sufficiently thick.Therefore, in some examples, the metal plating may be between 3 and 15microns thick.

In various examples, different metals may be used to create the plating.Generally, a metal that is both highly conductive and non-magnetic maybe used for the plating. In practice, metals such as copper, silver, andgold may be used for the plating. Other metals, or a combination ofmetals may be used as well. In some examples, a metal may be selectedbased on the metal's ability to adhere to the plastic surface of therespective portions.

As previously described with respect to FIG. 1C-1E, various surfaces maybe plated depending on the embodiment. In some examples, only thesurfaces that will interact with RF signals may be plated. In otherexamples, an entire surface of the respective portion may be plated. Inyet further examples, all (or a majority of) the external surfaces of arespective portion may be plated with metal.

At block 608, the method 600 includes assembling the split-blockassembly by coupling a bottom side of the first portion and a top sideof the second portion to form a seam. The coupling forms an electricalconnection between the first portion and the second portion and the seamdefines a center of a set of waveguides in the split-block assembly. Theset of waveguides may be configured to couple each array to at least oneof the at least one port. The two portions are coupled to each other byvarious means, including fastening by heat staking, welding, oradhesives, or physically coupled by screws, pins, clips, or other means.When coupled, the two portions may be electrically coupled to eachother. That is, at least the RF portions of the waveguide may have ametal portion in contact with the respective waveguide on the adjacentportion.

Additionally, the antenna may have a circuit board configured tointerface with the antenna. The circuit board may be configured tocouple signals into and out of the antenna. For example, components onthe circuit board may inject signals for transmission into the antenna.Additionally, the circuit board may also be configured to couplereceived signals out of the antenna. The circuit board may be mounted ona bottom portion of the antenna block, where the port of the antennablock is located. In some further examples, the circuit board may beelectrically coupled to the antenna block as well, via metal surfaces onon the circuit board and the antenna block.

It should be understood that arrangements described herein are forpurposes of example only. As such, those skilled in the art willappreciate that other arrangements and other elements (e.g. machines,apparatuses, interfaces, functions, orders, and groupings of functions,etc.) can be used instead, and some elements may be omitted altogetheraccording to the desired results. Further, many of the elements that aredescribed are functional entities that may be implemented as discrete ordistributed components or in conjunction with other components, in anysuitable combination and location.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the scope beingindicated by the following claims.

What is claimed is:
 1. A radar system comprising: a split-block assemblycomprising a first portion and a second portion, wherein the firstportion and the second portion form a seam, wherein the first portionhas a top side opposite the seam and the second portion has a bottomside opposite the seam; at least one port located on a bottom side ofthe second portion; a plurality of radiating elements located on the topside of the first portion, wherein the plurality of radiating elementsis arranged in a plurality of arrays; and a set of waveguides in thesplit-block assembly configured to couple each array to at least one ofthe at least one port, wherein the split-block assembly comprises apolymer and wherein at least the set of waveguides, the at least oneport, and the plurality of radiating elements comprise metal on asurface of the polymer.
 2. The radar system according to claim 1,wherein the polymer is formed by an injection molding process.
 3. Theradar system according to claim 1, wherein a top side of the secondportion and a bottom side of the first portion form the seam and whereinthe first and second portions are electrically coupled at the seam. 4.The radar system according to claim 3, wherein the top side of thesecond portion and the bottom side of the first portion each have arespective region that is covered with a layer.
 5. The radar systemaccording to claim 1, further comprising a circuit board physicallycoupled to the bottom side of the second portion.
 6. The radar systemaccording to claim 5, wherein the circuit board is electrically coupledto a metallic portion of the bottom side of the second portion.
 7. Theradar system according to claim 1, wherein the metal on the surface ofthe polymer is between 3 and 15 microns thick.
 8. The radar systemaccording to claim 1, wherein set of waveguides has a height, andwherein the seam is located at a center of the height of the waveguides.9. A method of forming a waveguide antenna unit comprising: forming afirst portion of a split-block assembly from a polymer, wherein thefirst portion comprises a plurality of radiating elements located on atop side of the first portion, and wherein the plurality of radiatingelements is arranged in a plurality of arrays; forming a second portionof the split-block assembly from the polymer, wherein the second portioncomprises at least one port on a bottom side of the second portion;forming a metal surface on at least a first region of the first portionand a second region of the second portion; and assembling thesplit-block assembly by coupling a bottom side of the first portion anda top side of the second portion to form a seam, wherein the couplingforms an electrical connection between the first portion and the secondportion, wherein the seam defines a center of a set of waveguides in thesplit-block assembly, and wherein the set of waveguides is configured tocouple each array to at least one of the at least one port, wherein atleast the set of waveguides, the at least one port, and the plurality ofradiating elements comprise metal.
 10. The method according to claim 9,wherein the first portion and second portion are each formed by aninjection molding process.
 11. The method according to claim 9, whereinthe first region of the first portion is on the bottom side of the firstportion and the second region of the second portion is on the top sideof the second portion.
 12. The method according to claim 9, furthercomprising physically coupling a circuit board to the bottom side of thesecond portion.
 13. The method according to claim 9, further comprisingelectrically coupling the circuit board to the bottom side of the secondportion.
 14. The method according to claim 9, wherein forming the metalsurface comprises forming a layer on the polymer, wherein the layer isbetween 3 and 15 microns thick.
 15. A radar system comprising: aradiating assembly comprising a plurality of portions, wherein eachportion comprises a polymer; a port formed in at least one of theplurality of portions, and located on a bottom side of the radiatingassembly; a plurality of radiating elements formed in at least one ofthe plurality of portions, and located on a top side of the radiatingassembly, wherein the plurality of radiating elements is arranged in aplurality of arrays; and a set of waveguides in the radiating assemblyconfigured to couple each array to at least one of the at least oneport, wherein the set of waveguides, the at least one port, and theplurality of radiating elements comprise metal on a surface of thepolymer.
 16. The radar system according to claim 15, wherein the polymeris formed by an injection molding process.
 17. The radar systemaccording to claim 15, wherein adjacent portions of the plurality ofportions are electrically coupled to each other.
 18. The radar systemaccording to claim 15, further comprising a circuit board physicallycoupled to the bottom side of the radiating assembly.
 19. The radarsystem according to claim 18, wherein the circuit board is electricallycoupled to a metallic portion of the bottom side of the radiatingassembly.
 20. The radar system according to claim 15, wherein the metalon the surface of the polymer is between 3 and 15 microns thick.